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SEM3 BIOSCIENCE > VISION > Flashcards

VISION Flashcards

1
Q

What pigment do rods use in the photoreceptor transduction cascade?

A

RHODopsin

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2
Q

What pigment do cones use in the photoreceptor transduction cascade?

A

Photopsin

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3
Q

Which vitamin is involved in rhodopsin synthesis?

A

vitamin A

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4
Q

what are the two molecules that form rhodopsin?

A

retinal (a.k.a retinaldehyde)

opsin

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5
Q

what is the difference between photopsin and rhodopsin?

A

There are 3 types of photopsin; I, II and III, all absorb different wavelengths of light

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6
Q

what is the light absorbing component of photopigments?

A

retinal

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7
Q

once retinal has absorbed light, which conformation will if be found in?

A

all TRANS retinal

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8
Q

what is the function of the opsin portion of the photopigment?

A

determines what wavelength of light is absorbed by retinal

binding of retinal

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9
Q

what wavelength of light is absorbed by rods?

A

498nm

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10
Q

what wavelength of light is abosrbed by red cone opsins?

A

564nm

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11
Q

what wavelength of light is absorbed by green cone opsins?

A

533nm

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12
Q

what wavelength of light is abosrbed by blue cone opsins

A

433nm

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13
Q

what in the structure of various opsin molecules determines which part of the light spectrum they will absorb?

A

amino acids that surround the retinal binding site

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14
Q

How do photoreceptors response to light exposure?

A

Graded hyperpolarisation e.g. if there is more light expsoure, there will be more hyperpolarisation

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15
Q

in the dark, how much glutamate do photoreceptors release into synapse with bipolar cells?

A

GLUTAMATE RELEASED IN ABUNDANCE

Glu is inhibitory at this stage

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16
Q

in the light, how much glutamate do photoreceptors release into the synapse with bipolar cells?

A

GLUTAMATE NOT RELEASED

Glu is inhibitory, therefore net excitation on post-synaptic bipolar cell

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17
Q

which photoreceptors are more sensitive to light?

A

Rods

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18
Q

what is the function of the horizontal cells?

A

provide antagonistic responses to photoreceptor activation via GABA @ outer plexiform layer

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19
Q

what is the function of amacrine cells?

A

Amacrine cells are inhibitory neurons, and they project their dendritic arbors onto the inner plexiform layer (IPL), they interact with retinal ganglion cells and/or bipolar cells

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20
Q

what is a ‘receptive field’ of a ganglion cell?

A

The area of the retina in which light absorption excites a single retinal ganglion cell

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21
Q

what is the ‘on-centre’ pathway?

A

pathway in which the synapse between a photoreceptor and bipolar cell is sign INVERTING i.e. glutamate in inhibitory to bipolar cell and pathway is excited when its light

22
Q

what type of glutamate receptors are found in the on-centre pathway?

A

sign inverting metabotrophic glutamate receptors

23
Q

what is the ‘off centre’ pathway?

A

pathway in which the synapse in the outer plexiform layer is sign CONSERVING i.e. glutmate is excitatory. Glu released in abundance when its dark, which excites off centre ganglion cells

24
Q

what type of glutamate receptors are found in the off-centre pathway?

A

sign conserving ionotrophic glutamate receptors

25
Q

what are the two continuums of colour axis differentiation?

A

Red - Green
Blue - Yellow

Cones of different colours side by side in receptive fields produce information on colour based on how inhibited/excited the central bipolar cell is

26
Q

axons from which half of the RETINAL field decussate at the optic chiasm?

A

NASAL

27
Q

axons from which half of the VISUAL field decussate at the optic chiasm?

A

TEMPORAL

28
Q

where do fibres of the optic tract terminate?

A

lateral geniculate nucleus of thalamus

29
Q

some fibres leave the optic tract and travel to the pre tectal nucleus. What are these fibres function?

A

afferent limb of pupillary reflex

30
Q

what is the structure/function of baums loop?

A

division of the optic radiation

transmits information relating to the SUPERIOR retinal field

Travels via the parietal lobe

31
Q

what is the structure/function of meyers loop?

A

division of the optic radiation

transmits information relating to the INFERIOR retinal field

Travels via the temporal lobe

32
Q

a lesion that blocks the optic nerve of that eye, resulting in blindness in that eye….

A

Anopia

33
Q

a lesion at the optic chiasm, causing temporal visual field defects in both eyes…

A

bitemporal hemianopia

34
Q

what is the a common cause of bitemporal hemianopia?

A

pituitary adenoma

35
Q

a lesion in the right/left optic tract, causing both nasal and temporal visual defects…

A

homonomous hemianopia

36
Q

a lesion affecting meyers loop…

A

upper homonomous hemiquadrantanopia

37
Q

a lesion effecting baums loop…

A

lower homonomous quadrantantopia

38
Q

a lesion in the primary visual cortex…

A

homonomous hemianopia with central sparring

39
Q

when light is in the centre of an ‘on centre’ cell, it is…

A

excited

40
Q

when light is in the centre of an ‘off-centre’ cells, it is…

A

inhibited

via lateral inhibition of horizontal cells

41
Q

when light is in the annulus/periphery of an on centre cell, it is…

A

inhibited

42
Q

when light is in the annulus/periphery of an off centre cell, it is…

A

excited

43
Q

what is myopia? how is it corrected?

A

shortsightedness- distant objects are blurred, near objects are seen clearly

corrected with concave lens

44
Q

what is hypermetropia? how is it corrected?

A

longsightedness- both far and near objects are blurred

corrected with a convex lens

45
Q

what is presbyopia? how is it corrected?

A

age-related longsightedness due to lens fibre deposition with age

convex lens correction

46
Q

what is astigmatism? how is it corrected?

A

non-spherical curvature of the lens, meaning refraction isn’t equal throughout

corrected using a spherical lens

47
Q

how is visual acuity tested?

A

snellen chart

48
Q

a patient records a snellen chart fraction of 6/40. what does this mean?

A

6 - how far away the patient is (m)

40 - how far away the average person would be to read the symbols

49
Q

what is the test for colour blindness?

A

ischihara test plates

50
Q

how are visual fields tested?

A

confrontation testing

goldman perimeter testing

51
Q

heterotropia, crossed eyes and squint are laymans terms for which visual condition?

A

Strabismus

52
Q

what is the medical name for ‘lazy eye’?

A

amblyopia

SEM3 BIOSCIENCE (13 decks)

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